It's interesting to me that Perl in a Nutshell is your must-have book. It's one of my least-used Perl references -- I think the only one I've used less is Advanced Perl Programming, because I simply haven't been doing much with most of what it covers. (Though, honestly, I really should sit down and read some parts of it more closely; I'd probably use it more if I were more familiar with it.)

My current must-haves are:

1. Perl Cookbook
2. Perl Pocket Reference
3. the Camel

I'd reverse the order of that list for starting out, though: The Camel is thorough and detailed. Once I was familiar with that, I came to rely more on the pocket ref as a memory jogger. The Cookbook is more of an algorithmic reference and memory jogger -- but if you don't understand the examples, you won't be able to apply them appropriately, so it's not a good starting point. I do use Nutshell occasionally, usually to doublecheck syntax and available methods for DBI.

Once I'm familiar with a book, I can easily turn to exactly where the information I want is. I can bookmark at arbitrary locations much more easily than in most softcopy formats. While I'm usually working in a windowed environment these days, that hasn't always been the case, and it's much easier to use an offline reference when you only have a single term. And you can't get softcopy signed. :)